Design and Experimental Study on Digital Speed Control System of a Diesel Generator

amaranthgymnophoriaElectronics - Devices

Nov 15, 2013 (3 years and 8 months ago)

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Research Journal of Applied Sciences, Engineering and
Technology

6
(
14
)
:
2584
-
2588
,
2013

ISSN: 2040-7459; e-ISSN: 2040-7467
© Maxwell
Scientific Organization, 2013

Submitted: December 28, 2012 Accepted: February 08, 2013 Published: August 10, 2013

Corresponding Author:

Fu
-
Hong Kuang, College of Power and Energy Engineering, Harbin Engineering University,
China,
Tel
.
:

13654580244

2584

Design and Experimental Study on Digital Speed Control System of a Diesel Generator

En-Zhe Song, Fu-Hong Kuang, Cong Yao and Jun Sun
College of Power and Energy Engineering, Harbin Engineering University, China

Abstract: This study proposed a kind of digital embedded controller for the diesel generator. Some digital circuit
such as single chip microprocessor have been used in the system, therefore it can control the diesel more efficiently
and accurately. Based on the theory analysis, a circuit card used in the control system has been developed by means
of development tools, such as Altium10, PCB99 and Multisim. Besides, the control program corresponding to PID
control algorithm has been used. The experiment results show that the controller is work well in the plateau low-
temperature environment and normal environment. We are sure that our embedded controller offers a wide scope of
application in the field of digital controllers in the diesel generator industry.

Keywords: Diesel generator, digital embedded controller, PID algorithm

INTRODUCTION

The role of the diesel engine speed controlling
system is that the diesel engine can be automatically
adjusted to ensure steady operation under a specified
speed by adjusting the fuel amount automatically, when
the diesel engine loads are changed.
Fuel Supply Quantity is decided by digital
controller, while injection timing is decided by the
gears of diesel engines. The
double closed loop
system
based on microcontroller has been developed. This
digital control system is made up of a regulating unit,
an
executive device
and a measurement unit. The real
speed value of diesel engine and some other
working
condition parameters
are measured by the measurement
unit. The principle of external control loop is following:
The speed error between the real speed value and the
goal speed value is computed and processed by the
regulating unit, to get an intermediate control signal
which is equal to the given fuel rack position. In the
inner feedback loop, the regulating unit rectifies the
rack position according to the position error which is
computed between the given fuel rack position and the
real rack position. The injection quantity is adjusted by
executive device. Thus the speed of diesel generator has
been controlled automatically. The algorithm of the
digital speed control system can be seen from Fig. 1.
The College of Power and Energy Engineering has
liaise with Shan Xi Diesel Engine Industry Corporation
to completes this project. This research want to find out
a way to make diesel generator work more steady and
economically. Compared with the traditional analog
electronics speed control system, digital control system
can bring down the cost of fuel and make the generator
react faster. The major indications in the control system
are transient speed regulation and speed recovery time.
Technical norm: The main target technology
indicators as shown intensity (Ma et al., 2008):

• Transient speed regulation ≤7%
• Speed recovery time ≤3s
• Steady state speed regulation 0-5%

The system functions as shown:

• Engine speed control
o Keep the diesel engine speed in a stabilized state
when the load is changed
o Make the real speed value follow the goal speed
value by adjusting the fuel amount
• Whole range fuel amount control
• Acceleration rate/deceleration rate (Ac/Dc Rate)
and steady state speed regulation is adjustable
• The goal speed value can be changed by changing
the state of buttons
• The diesel engine can be stopped by the governing
system
• The parameters of control and state can be real-
time displayed
• It has alarm function

CONTROL

STRATEGY

AND

PRINCIPLES

A precise dynamic simulation model for the diesel
generator is hard to be established because of the power
system is a highly nonlinear time varying system. in all
working conditions working environment is full of
noise and the temperature is range from -40~70°C Only
the basic control parameters are not enough with


Res. J. Appl. Sci. Eng. Technol., 6(14): 2584-2588, 2013

2585

Speed
Control
unit
executive
device
injection
pump
diesel
Rotating
speed sensor
Goal speed
value
Fuel rack
Position
sensor
Real speed
value
Generator
-
+
+
-
Rack
Control
unit


Fig. 1: The block diagram of digital control system

The analog
processing circuit
switch signal
Speed ​​signal
processing circuit
ADC
I/O
power drive
unit
Man-Machine
Interaction
unit
Alarm
output
PWM
CAN
I/O
MC9S12XEP100
ECT
Rack Displacement
Cooling water
temperature
Air press
Speed set
Speed up
Speed down
Stop
droop
Speed sensor
Other
input/output
Electrical
Actuator
Host
computer


Fig. 2: Entire system block diagram

all the working conditions especially work in the
plateau low-temperature environment. To get excellent
performance of stable and dynamic state, using non-
linear variable gains and dynamic gain adjustment can
be obtained under any working conditions. The digital
speed controller of diesel generator change the injection
quantity by change the rack position so as to keep the
diesel engine speed in a stabilized state when the load is
changed.
Two methods have been used for real-time
adjustment diesel engine control parameters. First, a
kind of adjustments has been made using the LCD and
three buttons -1 select buttons, 1 up buttons and 1 down
button. The controller has a built in user interface. And
the second, CAN bus communication protocol has been
embedded into the system so we can use the PC to
Calibration parameters and analyze data.

Controller hardware design: The hardware part of
ECU2-GK controller is mainly made up of the
processor MCU, the speed signal conditioning circuits,
analog signal conditioning circuitry, switch processing
circuit, power driven circuit, man-machine interface
and power components.
The MC9S12XEP100 has been selected as the
control chip. MC9S12XE family delivers 32-bit
performance with all the advantages and efficiencies of
a 16-bit MCU (MC9S12XEP100 User's Manual ver1.0,
Freescale Semiconductor, Inc., 2006).
The features of the control chip are as follows:

• XGATE co-processor capable for build virtual
peripherals and boost the overall performance
• Flexible programmable hardware emulated
EEPROM
• System integrity support with the memory
protection unit and supervisor/user modes
• S12X CPU at 50 MHz bus speed
• ADC 12-bit resolution and 3 μs conversion time
• Enhance Capture Timer (ECT)
• Pulse Width Modulator (PWM)

The structure of controller is shown in Fig. 2.
A Hall-type sensor is used as speed sensor. When
the teeth of the rotor, which is made of magnetic
material, alternately get through the gap of the
permanent magnet, there will be a variable magnetic
field acts on the Hall element (semiconductor material)
and then a pulse signal is generated by Hall voltage.
The Sine-Like signal is sent into the microcontroller for


Res. J. Appl. Sci. Eng. Technol., 6(14): 2584-2588, 2013

2586

countering after being converted by the speed
conditioning circuit, so the rotation speed can be
detected according to the number of pulses generated.
In the hardware circuit design, the components are
used to build the logic circuit, the output signal
automatically stops when the speed signal is lost, which
is to protect the diesel engine and prevent speeding.
The rack position sensor is integrated in the inside
of the actuator and generates a voltage signal between
0V and 5V, corresponding to the zero position and the
maximum position. The signal has been sent into the
microcontroller's ADC module after conditioning by
the circuit so as to get rack position.
A communications circuit is made up of the CAN
controller which is inside the microcontroller and the
external CAN transceiver. The host computer uses the
circuit mentioned above to communicate with the
controller, in order to exchange data including
controller parameters and diesel status parameters.

Control program design: The program is an important
part of the control system. The main program of the
control system is used to complete initialization of
hardware chip system and manage the control
processes. Tasks with lower requirements in real-time is
completed by the subroutine in the main program, such
as speed up and speed down, shutdown,
communication, failure handling, man-machine
interaction and control process. Tasks with higher
requirements in real-time such as speed calculate and
rack displacement feedback signal acquisition PID
computed output is realized by the interrupt control
mode. Detailed algorithm of PID c-means is proposed
by Song (2004) and Yao (2006).
The application program for the controller is
created by using the C language. Figure 3 shows the
flow chart of the main program. The process includes
the following steps: system Function initialize, control
parameter initialization, acquisition speed setting and
rack position, I/O port initialize, communication, Man-
machine dialogue subroutine, alarm processing.
In the main program, operation after power on the
system is following:
First, each module in the hardware is initialized
and then the control parameter of the control program
such as the PID parameters is initialized.
The target speed and the real rack position of the
diesel have be collected to provide an initial value for
the control process.
Enable interrupt program and make interrupt
program works.
Judge whether the communication request exits or
not in the main loop, if it exits the communication
program executes on time, carry on the man-machine
interaction to insure two-way data communication;
Start
System
initialization
Control parameter
initialization
Acquisition speed
setting, rack position
Enable interrupt
Communication
Man-machine dialogue
subroutine
Switching signal
acquisition
Alarm processing
subroutine
System other functions
Y
N
alarm
Y
N


Fig. 3: Main program flow chart

otherwise jump out of the suboutime; Judge whether the
information exits or not, if it exits the alarm subroutine
executes, or jump out of the subroutine.
There are main two interrupts used in the program,
i.e., periodic timer interrupt and input capture interrupt,
the former is used for execute relevant subroutine on
time and the host processor responses; the latter is used
for collecting the speed pulse signal and XGATE which
is the coprocessor responses, in this way it helps to
reduce the mutual interference among the interrupt and
the load of the main processor.
In the timer interrupt program, speed deviation is
obtained by calculating the actual rotation speed and the
target speed, then it is used as the input of speed loop
PID, to calculate the value of target rack position; the
rack position deviation is obtained by collecting actual
rack position, then PWM output is calculated and then
the actuator is adjusted to change the speed of diesel,
finally realize the regulation of closed-loop. In this
process, according to the actual rotation speed and load
conditions, the control parameters of PID and the


Res. J. Appl. Sci. Eng. Technol., 6(14): 2584-2588, 2013

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Interrupt
Context Saving
Interrupt
entry
Speed
Calculate
Rack displacement
acquisition
Set target
speed
Parameter
Correction
Condition
judgment
Controller
calculation
Actuator output
Restore interrupts
the scene
Interrupt
exports


Fig. 4: Interrupt program flow chart

maximum amount of oil should be dynamically
adjusted to insure that the diesel work in our expect
state. Interrupt program 1 flow chart can be seen in
Fig. 3.
In the input capture interrupt program, each pulse
interval time is calculated according to the capture
timer of the Microcontroller, the instantaneous speed of
diesel is obtained through the filtering algorithms
derived, then, the average speed of diesel which is
acquired through smooth calculations is used for the
calculation of speed loop PID. The interrupt process
can be seen in Fig. 4.

RESEARCH

OF

EXPERIMENTS

WITH

DIESEL

In order to verify the functionality of the controller,
ECU2 controller is used for the diesel sets generator of
D6114 type to carry on the experiment. The rated
power of this generator sets is 90 KW and its rated
rotate speed is 1500 rpm:

• Directly start without load in target speed: The
starting curve of the diesel in target speed, i.e., the
first target speed is 700 r/min (idle speed) and then


Fig. 5: The target speed is 700 rpm



Fig. 6: The target speed is 1500 rpm



Fig. 7: Add load and repeal load

Table 1: Experimental data

δ
d

(%)

τ

(s)

Add load

4.
0

2.0

Repal load

4.6

1.8


1500 r/min, can be seen in Fig. 5 and 6, in which
black line represents rotate speed. As can be seen
in the figure, the diesel starts quickly and has small
overshoot.
• Add load in target speed when the diesel is in
stable: As is shown in Fig. 7 and Table 1, 100%
load has been added when the speed is 1500 rpm.
Several seconds later, the speed come back in 1500
rpm. And then the load has been repeal, the speed
has been rise.


Res. J. Appl. Sci. Eng. Technol., 6(14): 2584-2588, 2013

2588

CONCLUSION

This research concerns electronic controllers which
effectively control diesel generators. The developed
system is capable of real-time controlling and is very
effective in responding to perturbation. The developed
embedded controller has the following characteristics.
First of all, it makes the generator work more efficiently
and accurately, the digital speed control system can
supply the demand of fine grade. Secondly, the host
computer can communicate with the controller at any
time. Finally, the diesel can be stopped immediately in
cases of emergency. We are sure that our embedded
controller offers a wide scope of application in the field
of digital controllers in the diesel generator industry.

ACKNOWLEDGMENT

This study was supported by the Harbin
Engineering University and Shan Xi Diesel Engine
Industry, China.
REFERENCES

Ma, X.Z., E.Z. Song and W.Z. Zhou, 2008.
Requirement and test method for speed governing
system of marine diesel engine. GB/T 3475-2008,
pp: 3-5.
MC9S12XEP100 User's Manual ver1.0, Freescale
Semiconductor, Inc., 2006, Retrieved from: www.
FreescaleSemiconductor.com.cn, pp: 45-56.
Song, E.Z., 2004. Design and experimental study on
all-electronic governor of large diesel engine. Ship
Eng., 28(3): 33-36.
Yao, C., 2006. Research for improving speed governing
performance of electronic-controlled diesel engine
by intelligent gain adjustment. Ship Eng., 47(2):
82-83.